1. Field of Invention
The present invention relates to self-locking connector/adapter interfaces or cable connector couplings. This type of coupling is normally comprised of a threaded nut to mate to an electrical connector, a tubular body with connector engagement features as required for a given connector, a locking device which interfaces between the nut and body and a method for retaining the parts in a fixed relation to properly mate with the connector. The coupling is also referred to as a back shell.
2. Description of Prior Art
Rachet Type
Since the early 1980's aircraft manufacturers and the military have sought to eliminate safety wiring, thread sealants and other methods of securing a threaded interface, under service conditions such as shock, vibration, "G" loading, etc., with a self-contained device. Adapter manufacturers responded with several designs to meet this need. Most required an increase in the overall diameter of the coupling with a corresponding increase in length. A few maintained the existing dimensions but they had the same problem as the others, minimal or sporadic locking contact points. This type of device was written into MIL-C-85049 in 1990.
All of the above incorporated a spring type device, located in the body or nut of the coupling with matching detents in the counterpart component. The spring was radially loaded perpendicular to the axis of the body centerline. One to three spring devices have been used. A single spring tends to force the coupling to an eccentric position opposed to the body. Three springs correct this but only have a contact or locking point every 120 degrees.
Another problem associated with these minimal contact locking couplings was that the pre-set assembly torque, set at assembly, could be unintentionally released under field use conditions through improper or rough handling of the assembly.
An example of this construction is seen in U.S. Pat. No. 4,793,821.
Anti-rotation Locking Type
In 1991, a coupling interface was developed to cure the above problems with the rachet type coupling, based on equally spaced radial contact (locking) points to eliminate eccentricity and with a manual release/engage feature. When engaged, this feature made the interface a true positive anti-rotation type device. To release the lock, it had to be an intentional act of the person needing to inspect or repair the cable assembly.
As with the rachet type, the dimensional envelope grew but still had spaced radial contact points. Spaced points transmit stress between the coupling and body by a segment type of finger, which if damaged or broken renders the entire assembly unusable.
A new problem, unique to this type of interface, is alignment of the locking elements. When the coupling is torqued to the required limit, the locking elements may not be aligned and the lock ring may not engage. This condition requires that the coupling ring be rotated until the lock ring can be engaged. This is acceptable as long as the rotation needed does not reduce or exceed the torque limits required for proper assembly function.
An example of this construction is seen in U.S. Pat. No. 5,192,219.